Patents relating to waveguides and couplings therefore include U.S. Pat. Nos. 2,825,060; 3,109,996; 3,146,410; 3,293,573; 3,431,515; 3,375,474; 3,483,489; 3,518,579; 3,555,553; 3,573,835; 3,732,508; 3,758,886; 3,942,138; 3,969,961; Re, 32,835, 4,533,884; 4,652,839 and 4,994,818 and United Kingdom Patent 1,402,624.